Conventionally, a card reader has been widely utilized which is structured to perform reading of magnetic data recorded in a card and/or recording magnetic data to a card. In an industry such as a financial institution where a card reader is utilized, so-called skimming, that is, a criminal attaches a magnetic head to a card insertion part of a card reader and illegally acquires magnetic data of a card by the magnetic head, has conventionally become a large issue. Therefore, a card reader has been proposed which includes a metal sensor for detecting that a magnetic head for skimming (hereinafter, referred to as a “skimming magnetic head”) has been attached to a card insertion part (see, for example, Patent Literature 1). In the card reader described in Patent Literature 1, the metal sensor includes a core formed of magnetic material and a pair of excitation coils and a detection coil which are wound around the core. The metal sensor is disposed in an inside of the card insertion part formed in a hollow shape.